Toroidal Continuous Variable Transmissions (“CVT”) are used to transmit rotational power from multiple sources, such as jet engines, to an electric generator. Toroidal traction drives use power rollers and toroids to translate rotational motion from the power rollers to a shaft by using the traction between the power rollers and the toroids. In order to generate sufficient traction between the toroids and the power rollers, an axial clamping force is applied to the toroids along an axis defined by the shaft thereby pressing the toroids against the power roller and allowing the power roller to transmit rotational power to the shaft. The input speeds from the multiple power sources generally vary within a certain speed range.
As the load on the shaft changes, the amount of axial clamping force required to maintain adequate traction between the power rollers and the toroids, and thereby ensure full power transmission to the shaft also changes. In some systems, the amount of clamping force required to maintain the traction can be predicted, and the clamping force can be gradually increased or decreased to compensate. In other systems, such as electrical generator systems, the load can change suddenly and unpredictably, requiring a fast response to maintain traction.
In one example, an axially loaded toroidal drive system uses a spring with a constant stiffness to provide a necessary axial loading force. In another example, an axial loaded toroidal drive system uses linear cam rollers to provide an adjustable axial load. Another example of an axial loading toroidal drive system uses a combination of a linear cam and a fixed spring to provide the axial load.